The present disclosure relates generally to the electrical, electronic and computer arts and, more particularly, to integrated sensors.
Advancements in microelectronics have facilitated the introduction of numerous applications that benefit society in many ways. In addition to mainstream applications in conventional consumer electronics, microelectronics can be utilized in remote areas of the population. Given the ever-increasing globalization of society, precise acquisition, (near) real-time processing and analyses of tremendous amounts of information are in high demand. One example is the use of sensors that can detect and provide relevant environmental information, such as, but not limited to, radiation levels, inorganic particles, biological entities, etc., to ensure safety, security, and stability of environmental control. In addition, with advancements in mobile technology, technological benefits have been achieved by integrating such sensors into personal devices to provide real-time and customized readout of information.
Conventionally, different types of sensors are fabricated for the detection of corresponding different types of materials/substances. For example, Geiger counters are used to detect radiation dose, using ionization produced in a Geiger-Müller tube, and provide a real-time and semi-quantitative readout. However, Geiger counters have limited success in measuring high radiation rates and in measuring the energy of incident radiation. Personal radiation dosimeters in the form of wearable badges and the like are available but cannot provide a real-time indication of radiation; rather, such personal radiation dosimeters provide an indication of accumulated radiation or total radiation dose received. Biosensors, which often combine a biological component with a physicochemical detector, depending on the type of material to be detected, often require a certain amount of time for readout due to the reaction/detection mechanism. Moreover, better resolution/sensitivity requires longer processing time, which sometimes involves special instruments only available in laboratories, thus limiting the portability of biosensors.
Solid-state sensors used as dosimeters, biosensors, and magnetometers offer features such as compactness, cost efficiency, easy integration with existing semiconductor processes, and good performance with respect to sensitivity and resolution. Most solid-state sensors are single devices that operate as the sensor and output unit at the same time. Additional circuit design is required to provide amplification of the sensing signal. Conventional MOSFET sensors have limited sensitivity and resolution due to the inability to amplify their output currents.
Bipolar junction transistors include emitter, collector and base regions. A biasing voltage applied between a base contact and an emitter contact allows control of collector current. Bipolar junction transistors can be employed as sensors, switches or amplifiers. The operation of heterojunction bipolar transistors, which are a type of bipolar junction transistors, is based on a bandgap difference between the emitter and base.